[PATCH] powerpc/64: system call implement the bulk of the logic in C fix

[Michal Suchánek]

On Tue, Jan 28, 2020 at 12:17:12AM +1000, Nicholas Piggin wrote:
> This incremental patch fixes several soft-mask debug and unsafe
> smp_processor_id messages due to tracing and false positives in
> "unreconciled" code.
> 
> It also fixes a bug with syscall tracing functions that set registers
> (e.g., PTRACE_SETREG) not setting GPRs properly.
> 
> There was a bug reported with the TM selftests, I haven't been able
> to reproduce that one.
> 
> I can squash this into the main patch and resend the series if it
> helps but the incremental helps to see the bug fixes.

There are some whitespace differences between this and the series I have
applied locally. What does it apply to?

Is there some revision of the patchset I missed?

Thanks

Michal
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>  arch/powerpc/include/asm/cputime.h | 39 +++++++++++++++++-------------
>  arch/powerpc/kernel/syscall_64.c   | 26 ++++++++++++++------
>  2 files changed, 41 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
> index c43614cffaac..6639a6847cc0 100644
> --- a/arch/powerpc/include/asm/cputime.h
> +++ b/arch/powerpc/include/asm/cputime.h
> @@ -44,6 +44,28 @@ static inline unsigned long cputime_to_usecs(const cputime_t ct)
>  #ifdef CONFIG_PPC64
>  #define get_accounting(tsk)	(&get_paca()->accounting)
>  static inline void arch_vtime_task_switch(struct task_struct *tsk) { }
> +
> +/*
> + * account_cpu_user_entry/exit runs "unreconciled", so can't trace,
> + * can't use use get_paca()
> + */
> +static notrace inline void account_cpu_user_entry(void)
> +{
> +	unsigned long tb = mftb();
> +	struct cpu_accounting_data *acct = &local_paca->accounting;
> +
> +	acct->utime += (tb - acct->starttime_user);
> +	acct->starttime = tb;
> +}
> +static notrace inline void account_cpu_user_exit(void)
> +{
> +	unsigned long tb = mftb();
> +	struct cpu_accounting_data *acct = &local_paca->accounting;
> +
> +	acct->stime += (tb - acct->starttime);
> +	acct->starttime_user = tb;
> +}
> +
>  #else
>  #define get_accounting(tsk)	(&task_thread_info(tsk)->accounting)
>  /*
> @@ -60,23 +82,6 @@ static inline void arch_vtime_task_switch(struct task_struct *prev)
>  }
>  #endif
>  
> -static inline void account_cpu_user_entry(void)
> -{
> -	unsigned long tb = mftb();
> -	struct cpu_accounting_data *acct = get_accounting(current);
> -
> -	acct->utime += (tb - acct->starttime_user);
> -	acct->starttime = tb;
> -}
> -static inline void account_cpu_user_exit(void)
> -{
> -	unsigned long tb = mftb();
> -	struct cpu_accounting_data *acct = get_accounting(current);
> -
> -	acct->stime += (tb - acct->starttime);
> -	acct->starttime_user = tb;
> -}
> -
>  #endif /* __KERNEL__ */
>  #else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
>  static inline void account_cpu_user_entry(void)
> diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
> index 529393a1ff1e..cfe458adde07 100644
> --- a/arch/powerpc/kernel/syscall_64.c
> +++ b/arch/powerpc/kernel/syscall_64.c
> @@ -19,7 +19,8 @@ extern void __noreturn tabort_syscall(void);
>  
>  typedef long (*syscall_fn)(long, long, long, long, long, long);
>  
> -long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
> +/* Has to run notrace because it is entered "unreconciled" */
> +notrace long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
>  			   unsigned long r0, struct pt_regs *regs)
>  {
>  	unsigned long ti_flags;
> @@ -36,7 +37,7 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
>  #ifdef CONFIG_PPC_SPLPAR
>  	if (IS_ENABLED(CONFIG_VIRT_CPU_ACCOUNTING_NATIVE) &&
>  	    firmware_has_feature(FW_FEATURE_SPLPAR)) {
> -		struct lppaca *lp = get_lppaca();
> +		struct lppaca *lp = local_paca->lppaca_ptr;
>  
>  		if (unlikely(local_paca->dtl_ridx != be64_to_cpu(lp->dtl_idx)))
>  			accumulate_stolen_time();
> @@ -71,13 +72,22 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
>  		 * We use the return value of do_syscall_trace_enter() as the
>  		 * syscall number. If the syscall was rejected for any reason
>  		 * do_syscall_trace_enter() returns an invalid syscall number
> -		 * and the test below against NR_syscalls will fail.
> +		 * and the test against NR_syscalls will fail and the return
> +		 * value to be used is in regs->gpr[3].
>  		 */
>  		r0 = do_syscall_trace_enter(regs);
> -	}
> -
> -	if (unlikely(r0 >= NR_syscalls))
> +		if (unlikely(r0 >= NR_syscalls))
> +			return regs->gpr[3];
> +		r3 = regs->gpr[3];
> +		r4 = regs->gpr[4];
> +		r5 = regs->gpr[5];
> +		r6 = regs->gpr[6];
> +		r7 = regs->gpr[7];
> +		r8 = regs->gpr[8];
> +
> +	} else if (unlikely(r0 >= NR_syscalls)) {
>  		return -ENOSYS;
> +	}
>  
>  	/* May be faster to do array_index_nospec? */
>  	barrier_nospec();
> @@ -139,8 +149,10 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
>  		regs->gpr[3] = r3;
>  	}
>  
> -	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE))
> +	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
>  		do_syscall_trace_leave(regs);
> +		ret |= _TIF_RESTOREALL;
> +	}
>  
>  again:
>  	local_irq_disable();
> -- 
> 2.23.0
>